Displacement of silicone oils from the hydrophobic surface by aqueous trisiloxane solutions

Kinetics of the displacement of silicone oils of different viscosity by the aqueous solution of trisiloxane from quartz capillaries from 4 to 7 mum in radius with the hydrophobized (methylnted) surface is investigated. The di splacement kinetics is described by Washburn's equation with the dynamic va lues of contact angles and bulk viscosities of the solution and oils. In th e case of displacing (by the solution) thin Oil films, which were prelimina rily deposited onto the capillary surface, the advancing meniscus of the tr isiloxane solution collects the column of oil from the film. The volume of the collected oil practically coincides with that of preliminarily deposite d film, which is indicative of the sufficient extent of displacement. The f ilm displacement rate is controlled by the surface diffusion of trisiloxane molecules over the hydrophobic surface under the oil film. The order of ma gnitude of the measured surface diffusion coefficients is equal to about 10 (-5) cm(2) s(-1).